Plate type heat exchanger

ABSTRACT

A plate heat exchanger for use as an evaporator in a refrigerator including a compressor, a condenser, an expansion valve and the evaporator which cooperate to perform a refrigeration cycle. The plate heat exchanger comprises a plurality of plates stacked on each other to define chambers of a refrigerant and chambers of a medium to be cooled, a refrigerant introduction passage means extending through the plates and provided with orifices for delivering the refrigerant from the refrigerant introduction passage means to the refrigerant chambers, and a refrigerant stirring member for stirring the refrigerant supplied into the refrigerant introduction passage means in the form of a wet steam to make the refrigerant uniform. In both of the case where the stirring member is provided and the case where it is not provided, a uniform refrigerant in the heat exchanger will be attained by providing a refrigerant inlet pipe at a lower part of one side of the heat exchanger thereof in which an inlet/outlet port for a medium to be cooled is provided and by providing a refrigerant outlet pipe at an upper part of the other side of the heat exchanger opposite to the above-noted one side thereby making the refrigerant flow in the heat exchanger smooth.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a plate heat exchanger and, in particular, to a plate heat exchanger for use as an evaporator in a refrigerator which includes a compressor, a condenser, an expansion valve and the evaporator which cooperate to perform a refrigeration cycle.

[0003] 2. Prior Art

[0004] A prior art plate heat exchanger will be explained with reference to FIGS. 5a and 5 b.

[0005]FIG. 5a is a schematic front view of a prior art plate heat exchanger which, as shown, includes a refrigerant inlet pipe 1, a refrigerant outlet pipe 6, a water (or brine) inlet pipe 10 and a water (or brine) outlet pine 16.

[0006]FIG. 5b is a cross-sectional view taken along a line A-A in FIG. 5a. As shown, wet steam of a refrigerant (i.e., a combination of a gaseous refrigerant and a liquid refrigerant) which is introduced into the heat exchanger through the refrigerant inlet pipe 1, flows through a refrigerant introduction passage 2 and orifices 3 into refrigerant chambers 4 whereby the refrigerant is subject to heat exchange with water (or brine) in water (or brine) chambers 7 via plates 7′ which form a partition between adjacent refrigerant chamber 4 and water chamber 7, and the refrigerant then flows into a refrigerant outlet passage 5 and finally exits the system through the refrigerant outlet pipe 6.

[0007] However, the prior plate heat exchanger suffers from the following problems.

[0008] The orifices 3 are arranged at predetermined intervals in a direction of the refrigerant introduction passage 2 in such a manner that each orifice 3 fluidly communicates the distribution passage 2 with one of corresponding refrigerant chambers 4. Thus, if the number of refrigerant chambers 4 is increased thereby causing the refrigerant introduction passage to become long, less gaseous refrigerant reaches the distal end of the refrigerant introduction passage since the gaseous refrigerant has a low specific gravity as compared with that of the liquid refrigerant. Consequently, the closer to the proximal end of the refrigerant introduction passage 2 the refrigerant chambers are, the lower is the ratio of a supplied fluid refrigerant to the gaseous refrigerant. Since the gaseous refrigerant emits heat as a function of its sensible heat, when a ratio of supplied fluid to gaseous refrigerant becomes low, a ratio of heat exchange effected on the basis of a latent heat of the fluid refrigerant in the refrigerant chambers near the proximal end of the refrigerant introduction passage 2 decreases, and the cooling capacity of the refrigerant chambers becomes insufficient. This leads to a decrease in heat transfer efficiency, cooling capacity, and COP of the heat exchanger decreases.

[0009]FIG. 6a is a front view of another type of a prior art plate heat exchanger and FIG. 6b is a side elevation view of the heat exchanger. As shown, the heat exchanger includes water (or brine) inlet/outlet ports 21, 22, a liquid refrigerant inlet/outlet port 23, and a gaseous refrigerant inlet/outlet port 24. The heat exchanger comprises a plurality of stacked plates and the spaces between them define either water (or brine) or refrigerant chambers. FIG. 7a shows a side of a plate constituting the heat exchanger which defines a water (or brine) chamber 29, and FIG. 7b shows a side of the plate which defines a refrigerant chamber 33. The plate includes a gaseous refrigerant inlet/outlet passage 25, a gasket 26, a space 27, a gasket 28, a liquid refrigerant inlet/outlet passage 30, and a water (or brine) inlet/outlet passage 31, 32. When the heat exchanger is used as a condenser, a gaseous refrigerant supplied through the gaseous refrigerant inlet/outlet port 24 is subject to heat exchange with a water (or brine) to form a liquid refrigerant and, then exits through the liquid refrigerant inlet/outlet port 23. The water supplied through the water (or brine) inlet/outlet port 22 is subjected to heat exchange with the refrigerant and, thereafter, exits the heat exchanger through the water inlet/outlet port 21 with its temperature having been raised by heat transferred from the refrigerant. Further, when used as a cooling device, the refrigerant supplied through the refrigerant inlet/outlet port 13 in the form of a wet steam is subjected to heat exchange with the water (or brine) to become a gaseous refrigerant and, then, exits the heat exchanger through the refrigerant inlet/outlet port 22. The water (or brine) subjected to the heat exchange with the refrigerant is deprived of its heat and, thus cooled, exits through the water inlet/outlet port. In the heat exchanger of this type, if the refrigerant leaks, it will flow outside the heat exchanger in the following manner. If the refrigerant leaks from the refrigerant passage 25 and/or 30 shown in FIG. 7a, the leaking refrigerant will enter the space 27 which is in communication with the atmosphere and, thus, there is no danger of the refrigerant contaminating water (or brine) in the water (or brine) chamber 29. Further, if the refrigerant leaks from the refrigerant chamber 33 shown in FIG. 7b, the leaking refrigerant will enter the space 27 which is in communication with the atmosphere and, consequently, the leaking refrigerant will diffuse without entering the water passage 31 or 32 through the gaskets 26 or 36, and consequently there is no danger of contamination of the water (or brine) by the leaking refrigerant.

[0010] In contrast, in a prior art plate heat exchanger as shown in FIG. 8, there is a danger that water will be contaminated by refrigerant leaking from the refrigerant passage or chamber. FIG. 8 is a front view of the heat exchanger which, as shown in FIG. 6, includes water inlet/outlet port 31, 32, a liquid refrigerant inlet/outlet port 33, and a gaseous refrigerant inlet/outlet port 34. As noted from FIGS. 9a and 9 b showing the opposite sides of a plate constituting the heat exchanger, the heat exchanger includes a gaseous refrigerant inlet/outlet passage 35, a water (or brine) chamber 39, a liquid refrigerant inlet/outlet passage 40, and water (or brine) inlet/outlet passages 41, 42, a refrigerant chamber 43, a sealing ring 44, and a collar 45. Although the mechanism of heat exchange of this heat exchanger is the same as that of the prior art heat exchangers of FIGS. 6a-7 b, if refrigerant leakage occurs, water contamination by the refrigerant will also occur, as explained below with reference to FIGS. 9a and 9 b.

[0011] Upon leakage of the refrigerant from the refrigerant passage 35 or 40 shown in FIG. 9a, it passes through an interface existing between the seal ring 44 and the heat exchanger plate which are joined together using brazing. Thus, the leaking refrigerant will directly enter the water (or brine) chamber 39 and contaminates the water (or brine). If the refrigerant leaks from the refrigerant chamber 43, except in the case that the refrigerant leaks through the collar 45, it will pass through the interface existing between the sealing rings 44 and the heat exchanger plate joined by brazing, and then directly enter the water passage 41, or 42.

[0012] In the light of the problems involved in the prior art heat exchanger, the present invention aims to provide a heat exchanger in which even if refrigerant leaks from a refrigerant passage and/or chamber, the refrigerant will move to the outside of the heat exchanger, thereby preventing water in the system being contaminated by the refrigerant.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is a schematic view showing a system of a refrigerator equipped with a plate heat exchanger in accordance with the present invention;

[0014]FIG. 2 is a schematic sectional view of a plate heat exchanger in accordance with an embodiment of the present invention;

[0015]FIG. 3a is an enlarged sectional view showing a refrigerant stirring member of a plate heat exchanger in accordance with another embodiment of the present invention;

[0016]FIG. 3b is an enlarged side elevation view of another type of the refrigerant stirring member;

[0017]FIG. 4a is a front view of a refrigerant stirring member in accordance with a further embodiment;

[0018]FIG. 4b is a side elevation view of the refrigerant stirring member of FIG. 4a;

[0019]FIG. 5a is a front view of a prior art plate heat exchanger;

[0020]FIG. 5b is a sectional view taken along a line A-A in FIG. 5a;

[0021]FIG. 6a is a front view of another type of a prior art heat exchanger;

[0022]FIG. 6b is a side elevation view of the prior art heat exchanger of FIG. 6a;

[0023]FIG. 7a shows a water (or brine) chamber defining side of a plate constituting the heat exchanger of FIG. 6a;

[0024]FIG. 7b shows a refrigerant chamber defining side of the heat exchanger plate of FIG. 7a;

[0025]FIG. 8 is a front view of a different type of a prior art heat exchanger;

[0026]FIG. 9a shows a water (or brine) chamber defining side of a plate constituting the heat exchanger of FIG. 8;

[0027]FIG. 9b shows a refrigerant chamber defining side of the heat exchanger plate of FIG. 9a;

[0028]FIG. 10a is a front view of another type of a heat exchanger in accordance with the present invention;

[0029]FIG. 10b is a side elevation view taken alone a line A-A in FIG. 10a;

[0030]FIG. 11a is a front view of a further type of a heat exchanger in accordance with the present invention;

[0031]FIG. 11b is a side elevation view taken along a line A-A in FIG. 11a;

[0032]FIG. 12 is a front view of a heat exchanger in accordance with another embodiment of the present invention;

[0033]FIG. 13 is a front view of a heat exchanger in accordance with a further embodiment of the present invention;

[0034]FIG. 14 is a diagram showing heat transfer rates of a heat exchanger of the present invention and the prior art heat exchangers;

[0035]FIG. 15a is a front view of a heat exchanger in accordance with an embodiment of the present invention;

[0036]FIG. 15b is a back view of the same heat exchanger plate;

[0037]FIG. 16a shows a water (or brine) defining side of a heat exchanger plate of a heat exchanger in accordance with an embodiment of the present invention;

[0038]FIG. 16b shows a refrigerant chamber defining side of the heat exchanger plate;

[0039]FIG. 17a is a front view of a sealing ring used in a heat exchanger of the present invention; and

[0040]FIG. 17b is a sectional view taken along a line A-A in FIG. 17a.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0041] With reference to the drawings, embodiments of the present invention will now be explained.

[0042]FIG. 1 shows a system of a refrigerator to be equipped with a plate heat exchanger in accordance with the present invention.

[0043] As shown, the refrigerator comprises an evaporator 11, a compressor 12, a condenser 13 and an expansion valve.

[0044] In the refrigerator, a liquid refrigerant is vaporized in the evaporator 11, the vaporized refrigerant is then compressed in the compressor 12 and thereafter cooled by a cooling water 15 in the condenser 13, to be liquefied, and the liquefied refrigerant is fed into the evaporator 11 through the expansion valve 14 with the pressure of the liquefied refrigerant being lowered by means of the valve, so that the refrigerant deprives the water (or brine) supplied from an inlet 10 of the evaporator 11 of its heat causing it to evaporate. The water cooled by heat exchange with the refrigerant exits the evaporator through an outlet 16.

[0045]FIG. 2 shows schematically a construction of a plate heat exchanger in accordance with the present invention. As shown, the heat exchanger includes a refrigerant inlet pipe 1, a refrigerant introduction passage 2, refrigerant inlet orifices 3, refrigerant chambers 4, a refrigerant exit passage 5, a refrigerant outlet pipe 6, water chambers 7 and a refrigerant stirring member 8 in the form of a cylinder. The refrigerant introduction passage 2 is defined by holes 7″ formed in plates 7′ defining the refrigerant chambers 4 and the water (or brine) chambers 7 therebetween, which holes are aligned with each other, and holes of sealing rings 3′ provided between the adjacent plates 7′, with the holes being coaxial with the holes of the plates 7′. The sealing ring 3 is provided with the orifice 3. The refrigerant exit passage is also defined by holes formed in the plates 7′ which are aligned with each other. The refrigerant stirring member 8 is connected to the refrigerant inlet pipe to enable the refrigerant stirring member 8 to receive a refrigerant and deliver the refrigerant into the refrigerant introduction passage 2 through a number of small holes 9 formed in the cylindrical wall of the refrigerant stirring member. Since the refrigerant is supplied into the refrigerant introduction passage 2 through the small holes, it is subject to turbulence and, as a result, is stirred.

[0046]FIG. 3a and FIG. 3b show respectively different types of refrigerant stirring member 8, each of which is provided with the small holes 9 provided such that the number of the small holes 9 decreases approaching the distal end of the stirring member 8. By this configuration, an area of opening of the small holes 9 decreases gradually from the proximal end to the distal end of the stirring member 8. As a result, a relatively large amount of refrigerant in the form of liquid can be fed into refrigerant chambers proximate to the refrigerant inlet pipe 1.

[0047] In the heat exchanger described above, a refrigerant in the form of a wet steam (namely, a mixture of a gaseous refrigerant and a liquid refrigerant) is supplied through the refrigerant stirring member 8 into the refrigerant introduction passage 2 to cause turbulence in the refrigerant in the passage 2, whereby the gaseous and liquid refrigerants are mixed uniformly. Then, the uniformly mixed refrigerant is introduced into the refrigerant chambers evenly and evaporated, thus ensuring that heat exchange effected in the heat exchanger is uniform across all of the refrigerator chambers. The vaporized refrigerant is discharged from the refrigerant outlet pipe 6.

[0048] The refrigerant stirring member 8 may be replaced with another type of stirring member as shown in FIGS. 4a and 4 b, i.e., a screw-type refrigerant stirring member 17 which imparts turbulence to the refrigerant passing through it.

[0049]FIGS. 10a and 10 b show a heat exchanger in accordance with another embodiment of the present invention. As shown, the heat exchanger includes a refrigerant inlet pipe 1, a refrigerant introduction passage means 2 provided with orifices (not shown) corresponding to the orifices 3 in the first embodiment, refrigerant chambers 4, a refrigerant exit passage 5, a refrigerant outlet pipe 6, water chambers 7, a water (or brine) inlet pipe 10, and a water (or brine) outlet pipe 16. This heat exchanger is characterized in that the refrigerant outlet pipe 6 is provided on the side of the heat refrigerator opposite to the side provided with the refrigerant inlet pipe 1.

[0050] In this heat exchanger, the wet steam of refrigerant introduced therein passes the refrigerant introduction passage 2, the orifices and the refrigerant chambers 4 and, finally, exits through the refrigerant outlet pipe 6 provided on the side opposite to the side provided with the refrigerant inlet pipe 1. In the heat exchanger as shown in FIG. 5, the refrigerant introduced therein is turned around to be directed to the refrigerant outlet pipe 6 which is provided on the same side of the refrigerator as the refrigerant inlet pipe 1 and, as a result, the gaseous refrigerant and the liquid refrigerant in the introduced refrigerant are likely to become separated under the inertia arising as a result of differences in their specific gravity. In contrast, in the heat exchanger of FIGS. 10a and 10 b, the refrigerant introduced therein flows smoothly without any turning around of the refrigerant, and thus separation stated above is unlikely to take place, thereby improving the rate of heat exchange.

[0051]FIGS. 11a and 11 b show a modification of the plate heat exchanger of FIGS. 10a and 10 b in which an additional refrigerant outlet pipe 6′ is provided on the side of the heat exchanger opposite the side provided with the refrigerant outlet pipe 6, whereby the flow of the refrigerant flowing into the refrigerant chambers can be made more smooth to thereby enable the refrigerant to be distributed evenly in the refrigerant chambers.

[0052]FIG. 12 shows a heat exchanger similar to that shown in FIG. 10a with an exception that the refrigerant inlet and outlet pipes 10 and 16 are provided on the side of the heat exchanger opposite the side on which, in the heat exchanger of FIG. 10a, the pipes are provided. FIG. 13 shows a heat exchanger similar to that shown in FIG. 11a with an exception that the refrigerant inlet and outlet pipes 10 and 16 are provided on the side of the heat exchanger opposite the side on which, in the heat exchanger of FIG. 11a, those pipes are provided.

[0053]FIG. 14 is a graph showing a rate x of heat exchange effected in the prior art heat exchanger of FIGS. 5a and 5 b and rates y and z of heat exchange effected in the heat exchanger of the present invention shown in FIGS. 10a and 10 b and in FIGS. 11a and 11 b in which graph the x-axis designates a quantity of heat (W/m²) and the y-axis designates a heat transfer rate. (W/m²K).

[0054] From this graph, it can be seen that by using the heat exchangers of the present invention a uniform refrigerant can be supplied into all of the refrigerant chambers evenly, thereby attaining higher heat transfer rates than those of the prior art heat exchanger.

[0055]FIG. 15a is a front view of a plate heat exchanger in accordance with another embodiment of the present invention and FIG. 15b is a rear view of the same. FIG. 16a shows a refrigerant chamber defining side of a plate constituting the heat exchanger, and FIG. 16b shows an opposite side of the plate for defining a water (or brine) chamber. Further, FIG. 17a is an enlarged front view of a sealing ring 46 used in the heat exchanger and FIG. 17b is a sectional view taken along a line A-A in FIG. 17a.

[0056] As is in the heat exchanger shown in FIGS. 8, 9a and 9 b, the heat exchanger of FIGS. 15a-17 b comprises water (or brine) inlet/outlet ports 31 and 32, a liquid refrigerant inlet/outlet port 33, a gaseous refrigerant inlet/outlet port 34, a gaseous inlet/outlet passage 35, water (or brine) chambers 39, a refrigerant inlet/outlet passage 40, water (or brine) inlet/outlet passages 41, 42, refrigerant chambers 43, sealing rings 46 and collars 45. The sealing ring 46 includes annular grooves 48 provided on the opposite sides thereof engaged with the surfaces of the adjacent plates, a passage 49 communicating the annular grooves provided on the opposite sides of the sealing ring. The plate includes passages 47 communicating the annular grooves of the sealing rings engaged with the opposite sides of the plate, so that refrigerant leaking into one of the annular grooves 48 can be led to the atmosphere through a passage formed from the passages 47, 49 and the annular grooves 48.

[0057] In the case that the refrigerant leaks from the refrigerant passages 35 or 40 shown in FIG. 16a, it will pass through the interface between the sealing ring 46 and the surface of the plate engaged with the ring 46. The leaking refrigerant will flow into the annular groove facing the plate surface, and will then flow through a passage defined by the passages 49 and the annular grooves 48 of the sealing rings and the passages 47 of the plates to reach the atmosphere and finally exits the heat exchanger without any contamination of the water (or brine) by entering the water (or brine) chambers passages. 

What is claimed is:
 1. A plate heat exchanger for use as an evaporator in a refrigerator comprising a compressor, a condenser, and the evaporator for performing the refrigeration cycle, said plate heat exchanger comprising: a plurality of plates stacked on each other to define chambers of a refrigerant and chambers of a medium to be cooled; a refrigerant introduction passage means extending through said plates and provided with orifices for delivering the refrigerant from the refrigerant introduction passage means to the refrigerant chambers; and a refrigerant stirring member for stirring the refrigerant supplied into the refrigerant introduction passage means in the form of a wet steam.
 2. A plate heat exchanger as set forth in claim 1, in which said refrigerant stirring member is a cylindrical member provided in said refrigerant introduction passage and extending in the longitudinal direction of the refrigerant introduction passage means, the cylindrical member having a proximal end for receiving the refrigerant in the form of a wet steam, a distal closed end, and a plurality of holes formed through the cylindrical wall thereof between the proximal end and the distal closed end so as to distribute the refrigerant into the refrigerant introduction passage means through the holes thereby stirring the refrigerant in the refrigerant introduction passage means.
 3. A plate heat exchanger as set forth in claim 2, in which a number of the holes formed in the cylindrical wall of the refrigerant stirring member gradually decreases in a direction from the proximal end towards the distal closed end of the refrigerant stirring member.
 4. A plate heat exchanger as set forth in claim 2, in which the opening area of the holes formed in the cylindrical wall of the refrigerant stirring member gradually decreases in a direction from the proximal end towards the distal end of the refrigerant stirring member.
 5. A plate heat exchanger as set forth in claim 1, in which said refrigerant stirring member is of a screw type and provided in the refrigerant introduction passage means so that the refrigerant passes through the screw type refrigerant stirring member is subject to a swirling motion.
 6. A plate heat exchanger used as an evaporator in a refrigerator comprising a compressor, a condenser, and the evaporator for performing a refrigeration cycle, said plate heat exchanger comprising: a plurality of plates stacked on each other to define refrigerant chambers for a refrigerant and medium chambers for a medium to be cooled, the plates extending in a vertical direction; a refrigerant introduction passage means horizontally extending through lower portions of said plates and provided with orifices for delivering the refrigerant from the refrigerant introduction passage means into the refrigerant chambers; a refrigerant inlet pipe provided on one side of the heat exchanger at a lower part thereof to introduce the refrigerant in the form of a wet steam into said refrigerant introduction passage means; and, a refrigerant outlet pipe provided at an upper part of the other side of the heat exchanger opposite to said one side to discharge the refrigerant passed through the refrigerant chambers outside the heat exchanger.
 7. A plate heat exchanger as set forth in claim 6, in which an medium inlet pipe is provided on the side on which said refrigerant inlet pipe is provided for introducing a medium to be cooled into said medium chambers and a medium outlet pipe is provided on the side on which said refrigerant inlet pipe is provided for discharging the medium from said medium chambers.
 8. A plate heat exchanger as set forth in claim 6, in which an additional refrigerant outlet pipe is provided at an upper part of said one side of said heat exchanger.
 9. A plate heat exchanger as set forth in claim 7, in which an additional refrigerant outlet pipe is provided at an upper part of said one side of said heat exchanger.
 10. A plate heat exchanger used as an evaporator or a condenser in a refrigerator comprising a compressor, the condenser, and the evaporator for performing a refrigeration cycle, said plate heat exchanger comprising: horizontal inlet and outlet passage means for refrigerant, the passage means being provided with vertical holes fluidly communicating the insides of the passage means with refrigerant chambers; horizontal inlet and outlet passage means for water or brine, the passage means being provided with vertical holes fluidly communicating the insides of the passage means with water or brine chambers; sealing rings for sealing said refrigerant inlet and outlet passage means from said water or brine chambers, said sealing ring being provided on its each side with a groove which is spaced away from the refrigerant in said refrigerant inlet and outlet passage means and from the water or brine in said water or brine chambers, said each side being engaged with corresponding adjacent one of the plates of said plate heat exchanger, said sealing ring being further provided with a passage fluidly connecting the grooves formed on the opposite sides of the sealing ring; and sealing rings for sealing said water or brine inlet and outlet passage means from said refrigerant chambers, said sealing ring being provided on its each side with a groove which is spaced away from the water in said water or brine inlet and outlet passage means and from the refrigerant in said refrigerant chambers, said each side being engaged with corresponding adjacent one of the plates of said plate heat exchanger, said sealing ring being further provided with a passage fluidly connecting the grooves formed on the opposite sides of the sealing ring; the plates of said heat exchanger being provided with through holes each fluidly connecting said grooves of said sealing rings which are positioned on and engaged with the opposite sides of the plate having the hole so that said holes of said plates, said grooves and passages of said sealing rings cooperate to define horizontal passages extending and finally leading to the atmosphere.
 11. A plate heat exchanger as set forth in claim 10 in which said horizontal passages leading to the atmosphere are provided with sealing members for preventing moisture in the atmosphere from entering into the plate heat exchanger.
 12. A refrigerator comprising a compressor, a condenser, and an evaporator for performing a refrigeration cycle, said refrigerator employing a plate heat exchanger as the condenser or the evaporator, said plate heat exchanger comprising: horizontal inlet and outlet passage means for refrigerant, the passage means being provided with vertical holes fluidly communicating the insides of the passage means with refrigerant chambers; horizontal inlet and outlet passage means for water or brine, the passage means being provided with vertical holes fluidly communicating the insides of the passage means with water or brine chambers; sealing rings for sealing said refrigerant inlet and outlet passage means from said water or brine chambers, said sealing ring being provided on its each side with a groove which is spaced away from the refrigerant in said refrigerant inlet and outlet passage means and from the water or brine in said water or brine chambers, said each side being engaged with corresponding adjacent one of the plates of said plate heat exchanger, said sealing ring being further provided with a passage fluidly connecting the grooves formed on the opposite sides of the sealing ring; and sealing rings for sealing said water or brine inlet and outlet passage means from said refrigerant chambers, said sealing ring being provided on its each side with a groove which is spaced away from the water in said water or brine inlet and outlet passage means and from the refrigerant in said refrigerant chambers, said each side being engaged with corresponding adjacent one of the plates of said plate heat exchanger, said sealing ring being further provided with a passage fluidly connecting the grooves formed on the opposite sides of the sealing ring; the plates of said heat exchanger being provided with through holes each fluidly connecting said grooves of said sealing rings which are positioned on and engaged with the opposite sides of the plate having the hole so that said holes of said plates, said grooves and passages of said sealing rings cooperate to define horizontal passages extending and finally leading to the atmosphere.
 13. A plate heat exchanger as set forth in claim 12 in which said horizontal passages leading to the atmosphere are provided with sealing members for preventing moisture in the atmosphere from entering into the plate heat exchanger.
 14. A plate heat exchanger comprising; a plurality plates stacked on each other so that the plates constitute a series of sets of two pairs of adjacent plates including a first pair of adjacent plates defining a first fluid chamber and a second pair of adjacent plates defines a second fluid chamber; first openings provided in said plates which are aligned with each other; second openings provided in said plates which are aligned with each other; first sealing rings each provided in said first fluid chamber in such a manner that the first sealing ring is aligned with said first openings and sealingly engages with the surfaces of the adjacent plates defining the first fluid chamber to allow a fluid in one of said second fluid chambers which are positioned on the opposite sides of the first fluid chamber to flow into the other of said second fluid chambers while preventing the fluid from entering into the first fluid chamber; second sealing rings each provided in said second fluid chamber in such a manner that the second sealing ring is aligned with said second openings and sealingly engages with the surfaces of the adjacent plates defining the second chamber to allow a fluid in one of said first fluid chambers which are positioned on the opposite sides of the second fluid chamber to flow into the other of said first fluid chambers while preventing the fluid from entering into the second fluid chamber; said first and second sealing rings being provided with annular grooves on their opposite sides which are sealingly engaged with said surfaces of said plates and encircle said first and second openings, respectively, in such a manner that said annular grooves are spaced radially outwardly away from said openings, each of said first and second sealing rings being further provided with a passage for connecting said annular grooves provided on the opposite sides thereof; a first conduit extending across each of said first fluid chambers to fluidly connect said annular grooves formed in the surfaces of said second sealing rings provided in said second fluid chambers positioned on the opposite sides of the first fluid chamber provided with the first conduit; and a second conduit extending across each of said second fluid chamber to fluidly connect said annular grooves formed in the surfaces of said first sealing rings provided in said first fluid chambers positioned on the opposite sides of the second fluid chamber provided with said second conduit; in which in the case that the fluid passing through said first sealing ring leaks through the interface between said first sealing ring and the surface of said plate engaged with said first sealing ring, the leaking liquid flows into said annular groove formed in the surface of the first sealing ring engaging with the surface of the plate and exits the heat exchanger through a passage defined by said annular grooves and passages connecting the annular grooves formed in said first sealing rings and said second conduits; and in the case that the fluid passing through said second sealing ring leaks through the interface between said second sealing ring and the surface of said plate engaged with said second sealing ring, the leaking liquid flows into said annular groove formed in the surface of the second sealing ring engaging with the surface of the plate and exits the heat exchanger through a passage defined by said annular grooves and passages connecting the annular grooves formed in said second sealing rings and said first conduits. 